1. Field of the Invention
The present invention relates to valves, and in particular, this invention relates to a pinch valve arrangement and piping system for flow control.
2. Description Prior Art
A pinch valve is essentially a flow control system with a flexible tubular conduit or sleeve connecting two sections of a piping system. This flexible tubular conduit is adapted to allow its sides to be pinched inward, reducing flow through the conduit. In this manner, a pinch valve sleeve effectively controls the flow of material through the valve and associated piping system.
Typical pinch valve sleeves are manufactured in many configurations, e.g., full port, cone, etc. Full port sleeves are the simplest to manufacture and in the fully open position provide an unobstructive passage equal to the full pipe diameter. However, when the port sleeve is throttled or pinched, due to the streamline shape of the sleeve, the throttled full port sleeve will cavitate at a relatively low-pressure drop across the valve. As the full port sleeve is a xe2x80x9chigh recoveryxe2x80x9d sleeve, it operates similar to a venturi.
As demonstrated in U.S. Pat. No. 5,992,818 to Jones et al., the flexible tubular conduit is centrally pinched in order to control flow through the elastic sleeve and into the remainder of the piping system. Similarly, U.S. Pat. No. 5,657,960 to Taylor illustrates the various devices that may be used to constrict or pinch the flexible sleeve. Further, as seen in U.S. Pat. No. 5,402,823 to Cole, a valve lever may be used to manually pinch the sleeve and restrict the flow therethrough.
In another typical pinch valve system, a flexible cone sleeve is utilized to control the flow of material through the valve. Basically, the flexible cone sleeve uses a gradually reduced-diameter cone on the inlet side of the flexible sleeve. Because of the additional turbulence generated at the downstream exit, the flexible cone sleeve arrangement has lower pressure recovery and allows a larger pressure drop across the valve before cavitation and cavitation damage occurs. For throttling or pinching service, it is common practice to use a valve body diameter equal to the pipeline diameter with a flexible cone sleeve selected to minimize cavitation yet still pass the required flow at the available pressure drop. For example, with a 36-inch line, the valve body would fit a 36-inch valve and the flexible cone sleeve may be 36 inches by 24 inches. In this example, the body, the mechanism, the actuator and sleeve are sized and designed accordingly.
While all of the prior art systems have the ability to control material flow through the valve body utilizing a pinching arrangement, the manufacturing cost and associated flow characteristics require significant improvement. Further, the full port sleeves cavitate at a relatively low pressure, necessitating maintenance, repair or replacement. Therefore, it is another object of the present invention to provide a pinch valve arrangement which prevents such cavitation and may be manufactured at a fraction of the cost of prior art systems.
The present invention is a pinch valve arrangement with primary application in the area of large diameter piping systems. The present invention includes a fixed conical reducer with an inlet end, an outlet end and an inside surface. The inside diameter of the inside surface gradually reduces from the inlet end to the outlet end of the fixed conical reducer, resulting in a conical-shaped inside surface. The inlet end of the fixed conical reducer is attached to an upstream pipeline. The pinch valve also includes a flexible full port sleeve with an inlet end and an outlet end; the inlet end attached to the fixed conical reducer outlet end, and the outlet end attached to the downstream pipeline. In a preferred embodiment, the outlet end of the full port sleeve is secured to a reducing flange, which, in turn, is secured to the inlet end of the downstream pipeline. Further, the present invention includes a pinching mechanism, i.e., an upper and lower pinch bar, for pinching or throttling the flexible full port sleeve.
In operation, the forward flow of fluid through the upstream pipeline is restricted in the fixed conical reducer before entering the flexible full port sleeve. As the diameter of the fixed conical reducer gradually decreases, the flow of material through the system is restricted. At the exit of the fixed conical reducer, the material enters the full port sleeve, and thereafter exits the system through a downstream pipeline. However, if the flexible full port sleeve is partially closed or pinched, the material flow is further restricted and controlled prior to its exit from the flexible full port sleeve into the downstream pipeline.
The invention itself, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.